To provide a polyvinyl alcohol polarization film giving high contrast, having little change in hue even when exposed to high temperature and exhibiting high durability, and a manufacturing method thereof.

A polarization film where iodine is adsorbed and oriented to a polyvinyl alcohol resin film and also a dichroic organic dye is contained is provided, and a polarizer where a transparent protective film is laminated to the polarization film is also provided. The polarization film is manufactured by a method comprising the following steps for the polyvinyl alcohol resin film: a swelling step for contacting with water; an iodine-dyeing step for dyeing in an aqueous solution containing iodine and potassium iodide after swelling; a boric acid-treating step for treating with an aqueous solution containing boric acid after iodine-dyeing; a washing step for washing in a solution mainly containing water after boric acid-treating; a stretching step for uniaxially stretching during or before the boric acid-treating step; and a dye-introducing step for introducing the dichroic organic dye during or before the washing step.